Rectifier.



H. K. SANDELL.

RECTIFIER.

' APPLICATION FILED MAR. 3 19M. 1,208,384. Patented Dec. 12, 1916.

4 SHEETS-SHEET I.

H. K. SANDELL.

RECTIFIER.

APPLICATION FILED MAR. 3. I914. 1,208,384. Patented Dec. 12,1916.

4 SHEETS-SHEET 2- H. K: SANDELL.

RECTIFIER.

APPLICATION FILED MAR. 3. I914.

Patented Dec. 12, 1916.

4 SHEETS-SHEET 4.

I /I/II/II/I111,151,515

UNITED STATES PATENT oFrroE.

HENRY K. SANDELL, or cmcaeo, rumors, Assmnon To HERBERT s. MILLS, or

omcaeo, rumors.

RECTIFIER.

Specification of Letters Patent.

Patented Dec. 12, 1916.

Application filed March 3, 1914. Serial No. 822,135.

To all whom it may concern:

Be it known that I, HENRY K. SANDELL, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Rectifiers, of which the following is a specification.

My invention relates to certain new and useful improvements in rectifiers and is fully described and explained in the specification and shown in the accompanying drawings, in which 7 Figure 1 is a longitudinal section through my improved device; Fig. 2 is an end view looking from the left of Fig. 1; Fig. 3 is a section on the line 3 of Fig. 1; Fig. 4: is a section on the line 1 of Fig. 1; Fig. 5 is a section through the stator on the line 5 of Fig. 1, and Fig. 6 is a circuit diagram.

Referring to the drawings, 7 generally indicates the stator which is of the type com mon in induction motors except for the windings hereinafter described. Mounted within the stator is therotor 8 carried by a shaft 9. The rotor is provided with the usual pole-pieces of radial form, main coils 9 starting-coils, and with the slip-rings 10 and 11 through which the current can be led in from the brushes. A centrifugal device for cutting out the starting coils is shown diagrammatically in Fig. 6 and this is, or may be of any desired construction. In the form shown, it consists of a conducting piece 12 having electrical connection with the slip-ring 11 and contacting with a pin 13 electrically connected with the starting coils which are shown at 1 1. WVhen the rotor is moving at the desired speed, the piece 12 moves away from the pin 13, cutting out the starting 0011s.

The parts thus far shown and described,

it will be seen, are those of the common induction motor in which the current is led to the rotor through sliprings, and the stator is of an induction type and carries the induced currents. This type of motor is highly advantageous for use ina rectifier of small size because it is self-starting, because it is very cheap and is thoroughly practical for small-sized devices. In using the device, however, for rectifying purposes, it must be got into step and must remain in step and, therefore, in some manner it becomes necessary to eliminate the slip which is the characteristic of induction motors. In other words, the induction motor must be made to run synchronously. This is accomplished by inserting into" the field or stator two coils 15 in series with each other and so wound as to produce localized fields of opposite polarity, which coils 15 are excited by the rectified current produced as hereinafter specified. The result of this construction is that there are provided in the stator, by means of the rectified current, localized poles, and it the commutator, hereinafter to be described,

the rotor shall run synchronously. Under this light load the slip would be very slight in any event and the'presence of the two fixed poles is suflicient to maintain synchrony.

The shaft at th e'left of the rotor is hollowed out to receive conductors 16 which carry the unrectified current. These conductors, it will be noted, are in parallel with the coils of the rotor. The shaft 9 has fixed upon it a. disk 17 carryingrtwo circular sets of segments, 18,19,20 and 21, arranged in two circles, and the evenly-numbered segments of the two sets being in electrical connection with each other and connected to one of the conductors 16, while the odd-numbered segments are likewise in electrical connection with eachother and connected to the other vice will be readily apparent from the description of its construction. The alternating-current is led in through the brushes on the slip-rings 10 and 11, energizing the main and starting'coils of the rotor. When the rotor is up to speed, which is nearly a synchronous speed, the slip being naturally very small, the current led out of the brushes bearing orl the commutator segments will alternate only very slowly. lit will obviously alternate only as often as the slip amounts to a quarter turn of the rotor. During. any one of the periods of flow of the current thus issuing from the commutator brushes, the

coils in the stator can become energized and establish localized poles in the stator, so that thereafter the rotor will run synchronously and thedirect current can be.

continuously drawn from the commutator brushes-and utilized in any desired manner as, for instance, in the motor which is shown diagrammatically in Fig. 6 as having connection therewith. Of course; as soon as the rotor is moving at a suficiently'high speed, its starting coils are cut out in the usual 'coils into its stator.

The mechanical structure, here shown is very simple and is peculiarly designed for rectifying currents of relatively-small volume. The motor is, or may be, of a type commonly sold on the market at a very low price, varied only by the introduction of the It requires no modification except the addition of these coils and the provision of the commutator at one end. Byperrnitting current to "flow direct from the slip-rings to the commutator-segments instead of through the armature,'a considerably greater volume of current can be rectified than could be safely passed through the armature. In the motor selected the rotor is the current because, by such part afi'ected by the alternating construction, the

we n necessary duced to the mlnimum.

'lt realize that considerable variation is possible in the details of the construction number of movable parts is re-- herein shown, and I do not intend to limit,

myself thereto,'except as pointed out in the following claim, in which it is my intention to claim all the novelty inherent in the device as broadly as is permitted by the state of the art.

all claim a's'new and desire to secureby Letters Patent A device of the character described comprising a motor of the inductionv type having a primary rotor and a secondary stator, a commutator, one member of which i is driven by the rotor, slip rings carried by the rotor, connections movable with the rotor from the slip rings to the rotor windlugs and from the slip rings to the driven commutator member, two windings in the secondary member, one of which is short circuited'and the other of which consists of coils, leads for drawing 03 rectified current from the-stationary Jmember of the commutator (and .for leading the rectified current therefrom to the coil'winding of the stator. I I A lln testimony whereof l have hereunto set my hand this 23rd dayof February, 1914.

' HENRY K. SANDELL. ln presence of two subscribing witnesses:

A. C. FISCHER, 1 JD. C. THonsEN. 

